Ultrasound diagnosis enables to display in real time how the heart beats or the fetus moves, by simply bringing an ultrasound probe into contact with the body surface. This technique is highly safe, and hence allows repeated examination. Furthermore, this system is smaller in size than other diagnostic apparatuses such as X-ray, CT, and MRI apparatuses and can be moved to the bedside to be easily and conveniently used for examination. In addition, ultrasound diagnosis is free from the influences of exposure using X-rays and the like, and hence can be used in obstetric treatment, treatment at home, and the like.
In addition, an ultrasound diagnostic apparatus is used not only for image diagnosis but also for an RFA (Radio Frequency Ablation) as a local treatment method for hepatocellular cancers, a biopsy which examines hepatocellular tissues, and the like. In such a treatment or examination, in order to accurately make a puncture in a region of interest by using a puncture needle, an ultrasound diagnostic apparatus is used to monitor the region of interest and the puncture needle in real time.
When, however, using a conventional ultrasound diagnostic apparatus for monitoring in a paracentesis, the following inconveniences occur.
First of all, when performing a paracentesis while monitoring a general ultrasound image provided by the conventional ultrasound diagnostic apparatus, the operator sometimes faces difficulty in seeing the needle due to the influence of the position of a lesion or the insertion angle of the needle. Under the current situation, the solution of such a problem largely depends on doctor's experience and knowledge. For example, the doctor indirectly grasps the position or the like of the needle while seeing the movement of the tissue when moving the needle.
In addition, as shown in, for example, FIG. 14, there is available a technique of performing ultrasound image monitoring in a paracentesis by generating an image C of a needle extracted by subtracting an image A obtained by oblique scanning (scanning with a beam angle being adjusted to make an ultrasound beam vertically strike the needle) from an image B obtained by general ultrasound scanning (without performing oblique scanning), and using the image obtained by adding the image A to the image C. In the use of this technique, however, when executing the above oblique scanning, grating lobes may occur depending on the beam shape and the like. This may lead to the generation of artifacts in an image. In addition, assume that oblique scanning is performed such that an ultrasound beam vertically strikes the needle. In this case as well, even a slight shift of the position of the needle from a scan slice may fail to preferably visualize the needle.
In consideration of the above situation, it is an object to provide an ultrasound diagnostic apparatus which can monitor a living body tissue and a puncture needle with a favorable high-quality image when performing a paracentesis, and a method of controlling the ultrasound diagnostic apparatus.